How Does Friction Affect Energy Conservation in Rotational Motion Experiments?

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SUMMARY

The discussion centers on the application of the conservation of energy principle in rotational motion experiments, specifically addressing the impact of friction. The equation presented is Ui + Kroti + Ktransi = Uf + Krotf + Ktransf + Wf, where Wf represents work done against friction, calculated as Tf = f * r. The confusion arises from reconciling energy loss due to friction with the conservation of energy, leading to questions about the correct formulation of the energy equation and the role of torque.

PREREQUISITES
  • Understanding of conservation of energy principles in physics
  • Familiarity with rotational dynamics and torque calculations
  • Knowledge of kinetic energy equations (both rotational and translational)
  • Basic grasp of frictional forces and their impact on mechanical systems
NEXT STEPS
  • Study the relationship between torque and energy in rotational systems
  • Explore the derivation of energy equations in the presence of friction
  • Learn how to calculate work done by friction in mechanical systems
  • Investigate the effects of different friction coefficients on energy conservation
USEFUL FOR

Students in physics, educators teaching rotational dynamics, and anyone interested in understanding the complexities of energy conservation in mechanical systems involving friction.

Painguy
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Homework Statement


We performed a small experiment in class which had us attach a mass to a string which hung on a pulley which led to a rotating object.
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We were then told to write down a conservation of energy equation stating that the initial energy is equal to the final energy. We were asked to include kinetic energy (rotational, translational), potential energy, and energy lost due to friction which we found with Tf=f*r.


Homework Equations




The Attempt at a Solution



This is what I have setup so far.

Ui +Kroti +Ktransi=Uf+Krotf +Ktransf +Wf

mgd=.5Iw^2 + .5mv^2 -f

I'm still a little confused about how energy is conserved if we're losing energy due to friction?

After that they ask me to replace every instance of w with v/r and v with 2d/t and try to get the following I=(mr^2)((gt^2/2d)-1-(t^2/(2md))f)

What am I doing wrong here?
 
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Painguy said:
mgd=.5Iw^2 + .5mv^2 -f
f is the force of friction? If so, there are two things wrong with the -f term.
 
how in the world are you equating torque with energy
 
haruspex said:
f is the force of friction? If so, there are two things wrong with the -f term.
I suppose I should have did f*Δd? I'm not sure what to do here.
 

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